PTC Genetic Taste Test

The ability to taste phenylthiocarbamide (PTC) is controlled by a single gene, TAS2R38, which codes for a bitter taste receptor. Variants of this gene determine whether individuals find PTC intensely bitter, slightly bitter, or tasteless. This simple Mendelian trait illustrates genetic variation, natural selection, and sensory perception.

1. Provide students with PTC paper strips (or similar safe substitutes used in genetics education).
2. Have each student place the strip on their tongue for a few seconds and record their perception (bitter, slightly bitter, or no taste).
3. Collect class results and group individuals as tasters, weak tasters, or non-tasters.
4. Discuss inheritance patterns, noting that tasting is a dominant trait.
5. Extend by comparing results to population averages (about 75% tasters, 25% non-tasters).
6. Explore environmental and physiological factors (e.g., dry mouth, prior food intake) that may influence results.

Do you have the bitter taste gene? | Science-U - wpsu:

📄 PTC The Genetics of Bitter Taste - Learn.Genetics: https://learn.genetics.utah.edu/content/basics/ptc/

• Compare PTC tasting with thiourea or PROP (propylthiouracil), other bitter-tasting compounds used in genetics studies.
• Investigate correlations between PTC tasting ability and food preferences (e.g., broccoli, coffee, dark chocolate).
• Conduct a family survey to create a pedigree chart and analyze inheritance.
• Relate findings to evolutionary biology by discussing survival advantages of bitter taste detection.

• Use only commercially prepared PTC paper intended for classroom use.
• Ensure students do not swallow the paper; it should be briefly tasted and discarded.
• Provide water for rinsing mouths after tasting.
• Screen for allergies or sensitivities before the activity.

• What does it mean genetically if someone can taste PTC? (They carry at least one copy of the tasting allele, T.)
• Why might non-tasters still exist if tasting bitter compounds is advantageous? (Heterozygotes may have selective advantages, or non-tasters may detect other bitter compounds.)
• How does PTC tasting demonstrate Mendelian inheritance? (Tasting is a dominant trait; non-tasters have two recessive alleles, tt.)
• What evolutionary purpose does bitter taste perception serve? (It helps avoid toxic plants and chemicals.)
• How might PTC tasting ability influence health choices? (Strong tasters may avoid bitter vegetables or tobacco products.)